22-02-2019, 11:21 PM
A 1929 Austin dwg on the old site gave tolerances as front -1/4 thou, rear + 1/4.
Tight fits certainly complicate matters and can lead to all sorts of damage. Many, "mechanics" included, inflict enough damage with standard fits. But tight fits reduce working clearance and every ten thou gained reduces the traditional Seven sound.
If new cranks are finished significantly larger, it may explain why bearing tolerances and clearances now not a major topic.
Those applying generous unmounted preload to a.c bearings must beware that if a tight fit on shaft, the preload will significantly further increase.
Modern tolerances seem more tight than older bearings.
Despite the claimed accuracy of micrometers, really accurate measuremnt requires skill and is seldom certain.
Tight fits certainly complicate matters and can lead to all sorts of damage. Many, "mechanics" included, inflict enough damage with standard fits. But tight fits reduce working clearance and every ten thou gained reduces the traditional Seven sound.
If new cranks are finished significantly larger, it may explain why bearing tolerances and clearances now not a major topic.
Those applying generous unmounted preload to a.c bearings must beware that if a tight fit on shaft, the preload will significantly further increase.
Modern tolerances seem more tight than older bearings.
Despite the claimed accuracy of micrometers, really accurate measuremnt requires skill and is seldom certain.